DESCRIPTION: (Applicant's Abstract) This application for a Mentored Research Scientist Development Award (RSDA) has been revised according to the suggestions of the Review Committee. The award will facilitate my career transition from sociology and program evaluation to drug abuse research. It will also offer the opportunity to concentrate my research energies on significant but under-researched research questions, and it will allow me to improve my statistical, methodological and other research skills. A ''multiple-mentorship'' approach will be utilized in that M. Douglas Anglin, Ph.D., Director of the UCLA Drug Abuse Research Center (DARC), will act as the primary mentor, and other scholars in psychology, sociology, and statistics at UCLA, and at DARC, will offer expertise in statistical, methodological and other research issues. The RSDA will be used to complete and extend research that systematically examines the potential causes and consequences of "vigilant" participation in treatment, using a treatment engagement theoretical model developed for the proposed investigation. The research design and methods of the proposed research utilize six research projects. Five of these projects involve prima data collection efforts in which the applicant is either the Principal or Co-Principal Investigator. The sixth study includes a secondary analysis of the Drug Abuse Treatment Outcome Study (DATOS). Secondary analyses of additional DARC datasets will be conducted as necessary. The research strategy is to use the primary analyses to answer the questions and the secondary analyses to triangulate and extend the findings of the primary analyses. Multivariate analyses including structural equations and hierarchical modeling of client and program predictors of treatment engagement and client consequences of engagement will be conducted. The empirical gaps and unanswered questions revealed by these analyses will be the basis for future research proposals that will be submitted during the RSDA period. One area that will be addressed in future research involves understanding how and why drug treatment works for some individuals, particularly those who fully engage in treatment. The proposed research will explore important hypotheses concerning the consequences of treatment engagement and the future research will investigate the most important empirical gaps on the topic. The proposed research will result in a number of empirical and theoretical contributions published in major scientific journals, and the findings conclusions, and implications of the entire body of work will be compiled in a six-chapter book.